It sounds like a cool project. I have suggestion for something to hold the medium in that could cost you nothing. I work at buffet, I was thinking of bring some of the empty fry oil contanier home and use to hold my targets when I shot other then at an range. maybe you could ask an eattery if you could have some. a good sharp razer blade can take the top off. I think the sides are to thick and can mess up your data. you could also ask if they have any old buckets (puddings, pickels and sometimes hard boided eggs come in them).